In recent years, high frequency wireless communication attracts increasing attention due to abundant spectrum resources thereof. For example, if frequency exceeds 6 GHz, bandwidth can reach 100 MHz. Such abundant spectrum resources are important to a future wireless broadband communications system. Therefore, a high frequency wireless communications technology has been considered as one of the most important technologies in next ten years.
Certainly, the high frequency wireless communication also has disadvantages, and one of them is an excessively large transmission loss. To make up this disadvantage, a beam forming technology is usually applied to increase receive power. In the beam forming technology, a sending party focuses transmit power in a particular direction by deploying a lot of antennas, to ensure a signal to noise ratio (SNR) of a receiving party. The transmit power focusing requires small beam dispersion, which leads to a narrow transmission range of a beam in the particular direction. In this case, even though a location of the receiving party changes a little, an error may occur in beam matching, and greatly affects receive power of the receiving party.
To discover the beam mismatching phenomenon in time, in the prior art, a BS usually periodically sends a reference signal (RS) to a UE by using different beams in sequence. The UE can know transmission quality of the different beams according to these periodic RSs.
However, in an actual case, there are a lot of beams used for uplink/downlink transmission between the BS and the UE. Therefore, the technical solution in the prior art in which the BS periodically sends an RS to the UE has low efficiency. If transmission quality of a beam currently serving the BS and the UE (serving beam, which is referred to as an active beam below) or a beam currently not serving the BS and the UE (non-serving beam, which is referred to as a standby beam below) deteriorates, the UE or the BS may take a long time to discover the deterioration, which greatly reduces reliability of wireless communication.